<；P>；PROBLEM TO BE SOLVED: To provide a gene therapeutic composition against malignant cancer cells by identifying a factor deciding the phenotype of cells such as the cancer cells and obtaining an intracellular antibody specific to the factor, and also an expression library and a method for screening the same. <；P>；SOLUTION: This intracellular antibody inhibiting (activating) the change of phenotype of the cells is obtained by a screening method comprising a process of constructing a heavy chain variable region (VHH) expression library by randomizing the part of sequence of the VHH of a camel heavy chain antibody, and determining the sequence of the randomized part by isolating the VHH in the cells of expressing the change of the phenotype in cultured cells transformed by using the expression library. By using the intracellular antibody, it is possible to identify an intracellular physiologically active substance controlling the phenotype of the cells, and provide a gene therapeutic composition of the cancer by using a vector expressing the intracellular antibody. <；P>；COPYRIGHT: (C)2008,JPO&INPIT
